diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 8d382d3abf38..7639dbf5d223 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -41,7 +41,7 @@
 
 /* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
 #define __PHYSICAL_MASK_SHIFT	46
-#define __VIRTUAL_MASK_SHIFT	48
+#define __VIRTUAL_MASK_SHIFT	47
 
 /*
  * Kernel image size is limited to 512 MB (see level2_kernel_pgt in
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index abde308fdb0f..c57a30117149 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -165,10 +165,7 @@ extern void cleanup_highmap(void);
 
 /* fs/proc/kcore.c */
 #define	kc_vaddr_to_offset(v) ((v) & __VIRTUAL_MASK)
-#define	kc_offset_to_vaddr(o)				\
-	(((o) & (1UL << (__VIRTUAL_MASK_SHIFT - 1)))	\
-	 ? ((o) | ~__VIRTUAL_MASK)			\
-	 : (o))
+#define	kc_offset_to_vaddr(o) ((o) | ~__VIRTUAL_MASK)
 
 #define __HAVE_ARCH_PTE_SAME
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 512ee87062c2..20e6a795e160 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -25,12 +25,7 @@
 #define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
 
 #define KERNEL_DS	MAKE_MM_SEG(-1UL)
-
-#ifdef CONFIG_X86_32
-# define USER_DS	MAKE_MM_SEG(PAGE_OFFSET)
-#else
-# define USER_DS	MAKE_MM_SEG(__VIRTUAL_MASK)
-#endif
+#define USER_DS 	MAKE_MM_SEG(TASK_SIZE_MAX)
 
 #define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index ec13cb5f17ed..b7c2849ffb66 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -127,7 +127,7 @@ EXPORT_SYMBOL(__strnlen_user);
 
 long strnlen_user(const char __user *s, long n)
 {
-	if (!access_ok(VERIFY_READ, s, n))
+	if (!access_ok(VERIFY_READ, s, 1))
 		return 0;
 	return __strnlen_user(s, n);
 }